The present invention is related to the delivery of medical electrical leads and more particularly to catheter delivery of such leads to a site in a right atrium of a heart in close proximity to the His bundle.
Various types of medical electrical leads have been developed for endocardial introduction into different chambers of a patient's heart. These flexible leads, various constructions of which are well known in the art, may be delivered using accessory tools, for example a stylet passing through a lumen of a body of the lead, or a catheter having a lumen through which the lead is passed.
A lead implanted in the right atrium can provide pacing therapy to preserve both atrial-ventricular synchronization and the normal ventricular activation and contraction patterns. However, pacing from a right atrial appendage, the typical pacing location in the right atrium, is ineffective if conduction between the right atrium and ventricles is blocked, for example at the AV node of the right atrium. Localized ischemia, inflammation, congenital defects, compression of the AV node, or ablation to prevent conduction as a treatment of atrial fibrillation can be the source of such a block. Ventricular pacing at an apex of the right ventricle is typically employed to bypass such a block, but recent studies have put forth the proposition that problems may arise from pacing at the right ventricular apex because an electrical impulse traveling from the apex moves contrary to the heart's natural conduction pathways. In light of these studies, methods for physiological pacing are currently under investigation; physiological pacing may be defined as stimulation of an intrinsic conduction system of a heart in order to preserve a natural conduction pattern of the heart.
A site of interest for physiological pacing is the His bundle, which is accessible from the right atrium. Existing catheters are not well suited for delivery of an electrical lead to the bundle of His, requiring protracted procedures to reach the desired location. The length of the procedure results in prolonged periods of time in an operating suit causing increased expense and difficulty for the patient as well as greater radiation exposure to the patient. In addition, existing catheters, to the extent they are able to deliver a lead to the His bundle, are generally parallel to the heart surface when they reach the location, making it more difficult to deliver and attach a lead to the underlying cardiac tissue. Thus, there is a need for a tool to facilitate delivery of a medical electrical lead to a site in the right atrium that is in close proximity to the His bundle, for either temporary or permanent pacing stimulation of the His bundle.